Regarding your m60 to m80 upgrade, did you find it worthwhile?
I'm torn between the two. If I do get the m80 I will probably have to put a stereo power amp for them. My AVR supports 6-8ohm.
Worthwhile is hard to measure. If you are torn I'd say go M80, otherwise you'll spend all of your time together wondering, "what if?". The difference when upgrading was about C$300 plus a loss of the 5% shipping discount because only two items were being sent in the second shipment (the discount originates from the shipping co). So if, like me, you always wonder "what if?" it makes financial sense to go all the way from the get go. For me the M60s were an experiment with the M82 concept (simulcast with M22s) which ended up as a marginal improvement not worth the hassle. Doing it this way allowed me to deal with both "what ifs?" at the same time. I also got a great pair of M22s for the computer set-up.
As for the AVR, almost all say 6-8 ohm and almost all have little problem with 4 ohm. It all depends on how loud you push them. I've played M80s with Sherwood Newcastle, Denon, and Yamaha to my loud listening levels with no problems (I live alone with the theatre in the basement, so no external restrictions).
Edited to add: I guess I should state that, although the M60s weren't really lacking anything, I believe the M80s are better speakers worth the extra ~$350. An extra $600? Maybe, maybe not.
